1. Field of the Invention
The present invention relates to a battery pack, and more particularly to, a battery pack that enables protective circuit boards coupled to a battery to have structures of high reliability and strong coupling forces.
2. Description of the Related Art
In recent years, compact and light portable electric and electronic appliances such as cellular phones, laptop computers, and camcorders are being actively developed and produced. Such portable electric and electronic appliances have embedded battery packs to allow operation even in places where there is no separate power source. Battery packs are currently employ chargeable and dischargeable batteries as they are more economical. Representative batteries include nickel-cadmium (Ni—Cd) batteries, Nickel-metal hydride (Ni-MH) batteries, lithium batteries, and lithium ion secondary batteries.
In particular, lithium ion batteries have operational voltages around three times higher than those of nickel-cadmium batteries or nickel-metal hydride batteries and are widely used as power sources for portable electronic appliances. In addition, lithium ion batteries are also widely used due to their relatively high energy density per weight.
In a lithium ion secondary battery used in a laptop computer, a plurality of battery cells are connected in series or in parallel in view of the increased power consumption and use time.
In this case, the lithium ion secondary battery for a laptop computer may be realized by a battery pack attachable to and detachable from the laptop computer.
Battery packs have various shapes according to the sizes and efficiencies of laptop computers with which the battery packs are used Since the laptop computers generally have very thin shape, the battery packs are also formed such that they have thicknesses within the thicknesses of the laptop computer.
Further, the battery packs that are detachably mounted to the laptop computers have protective circuits controlling the flows of currents of the batteries as the batteries become overheated, overcurrented, overcharged, overdischarged, or otherwise deteriorated.
In particular, a battery pack for a laptop computer generally employs a plurality of lithium ion secondary batteries, which has an increased possibility of danger. Accordingly, a smart protective circuit having more functions than a general protective circuit controlling one lithium ion secondary battery is mounted to such a battery pack. As the smart protective circuit has diversified functions, its mounting area becomes larger, in which case it occupies a considerable volume inside the battery pack.
In particular, a large amount of current flows through a connector of a battery pack that is connected to a contact portion of a battery of a laptop computer. The connector occupies a considerable space inside the battery pack.
Accordingly, a smart protective circuit is separated onto a board to which a connector is attached and a board to which a protective circuit is attached, in order to more efficiently utilize the interior space of a battery pack.
The separated boards are electrically connected to each other by an electric wire, and a current of up to several tens of Amperes flows through a portion of the electric wire to form a high current path between a positive electrode and a negative electrode of a battery.
However, if the electric wire is not big enough to allow sufficient current to flow, its resistance increases potentially causing overheating of the lithium ion secondary battery due to the obstructed current flow, which can cause explosion or deterioration of the battery. In addition, the coating of the electric wire may be melted by emission of heat, causing a short circuit with other signal wires. In this case, the protective circuit malfunctions or suffers damage, causing decrease of the reliability of the battery pack.
Moreover, the electric wire connecting the separated boards needs to have a sufficient coupling force so as not to be separated from the boards even when the boards are bent or the like in the process of assembling the battery pack.